Algerian special forces are continuing to hunt Islamist militants who overran a BP gas plant, as freed British hostages headed home.

As the stand-off at the remote desert facility entered a fourth day it was thought that around 10 British workers remained "at risk".

The Algerian state news agency APS reported on Friday night a "provisional" figure of 12 foreign and Algerian workers who had been killed in the fighting at the plant at In Amenas.

Among them are one Briton, one Frenchman - named by France's Foreign Ministry as Yann Desjeux - and one American, Frederick Buttaccio.

The news agency said about 100 foreign workers had been released from a total of 132 seized by the militants - along with 573 local employees.

Eighteen of the militants were also reported to have been killed - suggesting that around a dozen of the original group of about 30 could still be at large.

Footage of several British workers said to have escaped the siege has been shown on Algerian state television.

One man, who gave his name as Darren Matthews, said: "I feel safe at the moment but I won't feel 100% happy until I'm back in the UK, until I see my family."

He said: "My heart goes out to the guys that are still there and hopefully everyone comes home safe because, at the end of the day, it's only work, you know. No one should have to go through all this for a job."

Another of the four Britons who spoke said: "I think they did a fantastic job, I was very impressed with the Algerian army.

"I feel sorry for anybody who has been hurt."

A third man said that the Algerian army had "beaten the bad guys".

Irishman Stephen McFaul, who managed to flee from the al Qaeda-linked kidnappers is expected to be reunited with his family later.

The 36-year-old father-of-two from west Belfast is understood to have been able to escape when a vehicle he was in crashed after being attacked by the Algerian army - despite having explosives placed around his neck.

The militants, believed to be under the command of the al Qaeda-linked terrorist Mokhtar Balmokhtar , carried out their dawn raid on the plant on Wednesday morning.

Belmokhtar, is a one-eyed Algerian terrorist, known as The Uncatchable, who specialises in hostage taking and has strong links with al Qaeda in the Islamic Maghreb (AQIM).

Algerian forces launched their rescue mission early on Thursday fearing an "immediate threat" to the hostages.

The group is said to be demanding the release of two terror figures held in the US, including the 1993 World Trade Centre bombing mastermind Omar Abdel Rahman, in return for American hostages.

The US state department spokeswoman, Victoria Nuland, responded saying: "The United States does not negotiate with terrorists."

After chairing a meeting of the Cobra emergency committee, the Prime Minister told MPs that the situation in Algeria was "continuing" but he hoped it would be resolved shortly.

He said the attack on the complex was "large, well co-ordinated and heavily armed" and appeared to be pre-planned.

He also met the outgoing US defence secretary Leon Panetta and the pair discussed the need to work together to defeat al Qaeda in the Islamic Maghreb.

A British plane carrying a "diplomatic team" has arrived in Algeria around 280 miles from the hostage scene.

Meanwhile a US plane is beginning the process of evacuating its citizens, and other nationalities.

The Algerian rescue attempt was launched without consultation with the UK. Mr Cameron was only informed it was under way when he spoke to the Algerian prime minister.

Algerian communications minister Mohamed Said Belaid said the military operation succeeded in "neutralising a large number of terrorists and freeing a large number of hostages".

He added: "But unfortunately, we are sorry to say, there were some deaths and injuries."

The militant group behind the raid Katibat Moulathamine, or The Masked Ones, said it was retaliating for French military intervention against al Qaeda-backed rebels in neighbouring Mali.